A passenger conveyor typically includes a number of passenger platforms or steps which are driven in an endless path between horizontally spaced landings. Commonly, a combplate is mounted at the landings to permit passengers to easily step on or off the conveyor.
During the course of operation of a passenger conveyor, it is possible for a foreign object, such as the pointed heel of a woman's shoe, miscellaneous refuse, or, more dangerously, a body part of a passenger, to become lodged between a step and the combplate. Trapped foreign objects are forced against the combplate by the powerful mechanism which drives the conveyor, and a risk of harm is created for passengers as well as possible damage to the conveyor.
One approach to solving this problem has been to construct a movable combplate. Rather than resist the force generated by the obstruction to the motion of the conveyor, the movable combplate is displaced and closes a circuit which, in turn, deenergizes the conveyor. While the idea of a safety power-cutoff for a passenger conveyor has proved modestly successful, there exist numerous defects int he actual implementation of such a scheme.
Particularly, due to the environment in which many conveyors are utilized, the combplates are subjected to the deposits of a plethora of debris, including, for example, chewing gum, paper wrappers, soda pop, and the like. When the debris accumulates between the movable combplate section and the contact for the power cutoff switch, the movable section becomes jammed and physical contact with the switch is prevented to render the device inoperable.
Another problem which exists with existing movable combplate proposals is the difficulty in maintaining the position of the combplate when the conveyor is activated. Local construction codes commonly mandate certain performance capabilities which a public conveyor must meet. One such requirement is that the combplate maintain a specified degree of engagement with the steps of the conveyor at all times to prevent articles form being pulled below the combplate by the drive mechanism. The lodging of any foreign matter between the steps and the combplate tends to force the combplate upwardly and out of engagement with the steps. Accordingly, an approved safety device must provide for a hold down force to restrict relative displacement of the combplate and the steps. Existing types of clamps and related combplate hold downs tend to restrict the rearward motion of the combplate and thus minimize the effectiveness of the safety device.